Among the goals of the Human Genome Project are the development of physical and genetic linkage maps of each human chromosome. Genetic linkage mapping and physical mapping of chromosome 18 is substantially behind that of many other chromosomes. Nonetheless, a number of investigators have undertaken a major research effort in mapping this chromosome. These investigators have developed new resources, such as somatic cell hybrid panels for regional mapping, YAC and cosmid libraries, and new restriction fragment length polymorphisms, which will be useful for mapping studies. Unfortunately, the exchange of information between investigators is limited, and no attempt has been made to integrate these efforts. Thus, to begin to collate mapping data, to integrate genetic and physical maps, to identify resources that will promote mapping efforts, and to promote collaborations among investigators who have an interest in this chromosome, we propose an International Workshop on Chromosome 18 to be held in Chicago on July 13-14, 1992. The Aims of the Workshop are: 1. To prepare consensus genetic and physical maps of chromosome 18. 2. To prepare detailed physical maps in selected areas of chromosome 18: the DCC and BCL2 regions. 3. To begin to assemble a collection of DNA markers, preferably in the form of sequence tagged sites (STSs), along the length of the chromosome, which will be used as reference markers for further physical and genetic mapping of chromosome 18. 4. To assess the resources available for mapping, and to foster collaboration among interested investigators. 5. To interface with the chromosome 18 committee of the Human Gene Mapping Workshops, and with the CEPH and Eurogem representatives for chromosome 18.